1. Field of the Invention
The present invention relates to a method for manufacturing an organic EL display device including a plurality of organic EL elements.
2. Description of the Related Art
Organic EL display devices, which are of self-emission type, are attracting attention as a type of flat panel display. An organic EL display device refers to a display device using as a display element an organic EL element including a pair of electrodes and an organic compound layer between the electrodes. For displaying color images, the organic EL display device may have a structure in which organic EL elements that emit white light and color filters for different colors are combined, or a structure in which a plurality of types of organic EL elements that emit different colors, such as red, green and blue lights, are arranged.
In an organic EL display device including a plurality of types of organic EL elements, different organic compound layers are formed for the different types of organic EL elements. Accordingly, each organic compound layer is selectively formed at a predetermined position by vacuum vapor deposition using a metal mask.
Nowadays, since high-definition display devices are being increasingly developed, it is required that such organic compound layers be formed with a high precision. However, vacuum vapor deposition using a metal mask has problems, for example, with working accuracy in the formation of the metal mask and with the distortion of the metal mask resulting from radiant heat generated during vapor deposition, and these problems make it difficult to produce high-definition display devices.
For selectively forming organic compound layers with a high precision, Japanese Patent Laid-Open No. 2003-36971 discloses a method for patterning an organic compound layer by photolithography. More specifically, a first luminescent layer is formed over the entire surface of a substrate by coating, and then a photoresist layer (release layer) is formed on the first luminescent layer. The photoresist layer is patterned by photolithography so as to remain in the region where the first luminescent layer will be formed, and then, the first luminescent layer is patterned using the photoresist layer as a mask. Subsequently, a second luminescent layer is formed by coating over the entire surface of the substrate on which the patterned first luminescent layer is disposed. Then, the photoresist layer and the portions of the second luminescent layer overlying the photoresist layer are separated (lifted off) together. In this process, the first and second luminescent layers that emit different hues from each other can be selectively formed with a high precision.
In Japanese Patent Laid-Open No. 2003-36971, the second luminescent layer is formed over the entire surface of the substrate by spin coating. Therefore, the second luminescent layer continuously covers the entire surface of the photoresist layer. When the substrate is immersed in a solution for dissolving the photoresist layer in order to lift off the second luminescent layer and the photoresist layer, however, the solution enters through defects of the second luminescent layer or penetrates the second luminescent layer to reach the release layer. Therefore, the solution for dissolving the photoresist layer cannot come into contact with the release layer efficiently to dissolve the release layer stably. This causes the increase in tact time and the decrease in yield.